This invention relates generally to a vision panel providing a window in a fire door. More particularly, the present invention provides a vision panel providing simplified assembly.
Vision panels for fire doors provide a window through the fire door that preserves the integrity of the fire door by retaining an approved wire glass even after prolonged exposure to fire and possible thermal shock caused by the glass being sprayed with a fire hose after heating.
Currently available vision panels provide frame halves that may fit into the opening of the door from either side of the door. The frame halves have flanges which abut the front and rear faces of the door and inner sash members extending in from the flanges and which come together about a pane of glass to support the glass therebetween. Assembly of the vision panel can require two people, one to hold one frame half against one side of the door, while the second person from the other side of the door positions the glass and installs screws holding the frame halves together. In some designs the screws must pass through the door itself requiring accurate drilling of holes and raising the risk of splintering the door skin material.
U.S. Pat. No. 4,550,542, filed Aug. 9, 1984, and assigned to the assignee of the present invention and hereby incorporated by reference, describes an improved vision panel frame providing simplified installation by using bolts passing wholly through the precut window opening and a spring clip that may be used to hold one-half of the frame in position while the installer works from the other side of the door.
The spring clip in the '542 patent has a finger at one end engaging a portion of a sash member of the frame half to be retained, and a hook at the other end that may grip the edge of the window opening cut in the door opposite the installed frame. A second frame half is then installed over this hook covering it from view.
Care must be taken when tightening the screws holding the frame together to provide sufficient force to compress the sash against the glass so that should the glass become molten, the edges of the sash will embed themselves in the glass to hold it in position. Too much force in tightening the screws holding the frame together, however, can distort the metal frame halves.
Separate support elements may be placed underneath the glass pane during installation to support it above the lower sill of the opening centered within the sash plates.